We have undertaken a program to develop implantable left and right ventreicular assist devices (LVAD & RVAD) that can provide long-term support for the circulation. Our blood pumps are made from thermoplastic polymers by vacuum forming techniques. We can use vacuum formed valves or commercially available prosthetic valves. The pumps are driven pneumatically by transcutaneous air drive lines connected to either the Utah Heart Driver or the Heimes light-weight portable driver. The LVAD's and RVAD's are being tested in mock circulation studies to evaluate pumping performance characteristics and durability. The use of a new automated vacuum forming machine gives the capability of reproducing high quality, low cost pumps. Initial work to impregnate the blood chamber intima with herparin is promising. Although designed and successfully tested for human fit, our L/RVAD's have been modified to be implanted in sheep. To date, ten blood pumps have been implanted with the longest survivor living 18 days. We propose to embark on a comprehensive program of L/RVAD evaluation. Durability studies of the pumping chambers and valves will continue to validate their long-term integrity and indicate necessary improvements in their design and manufacturing. The work on heparin impregnation in blood pump intimas will continue. We will prove that our L/RVAD's can adequately support the circulation using an "Incremental Progressive Success" approach to animal implantation experiments with sheep. All animals will be instrumented for physiological studies of heart-L/RVAD hemodynamic interaction. More involved physiological studies will occur in some animals to examine hemodynamic and energetic characteristics of the hearts prior to L/RVAD implantation, after assist pumping, during induced left heart failure, and following L/RVAD removal. Pulmonary function tests will check for interference effects by the blood pumps. Hematologic studies will be run concurrently to characterize the response to L/RVAD implantation, including new assays for B-thromboglobulin and Platelet Factor 4. With this comprehensive testing program, we hope to achieve our goal of developing devices that can provide long-term support for the failing heart, and yet be compatible with eventual recovery of natural cardiac functioning.